source: dassfooter/trunk/daemon.py@ 1105

Last change on this file since 1105 was 980, checked in by hmueller, on Mar 16, 2012 at 11:16:51 AM

dassfooter (make html from out of plain mails

  • Property svn:executable set to *
File size: 2.8 KB
Line 
1#!/usr/bin/env python
2
3import sys, os, time, atexit
4from signal import SIGTERM
5
6class Daemon:
7 """
8 A generic daemon class.
9
10 Usage: subclass the Daemon class and override the run() method
11 """
12 def __init__(self, pidfile, stdin='/dev/null', stdout='/dev/null', stderr='/dev/null'):
13 self.stdin = stdin
14 self.stdout = stdout
15 self.stderr = stderr
16 self.pidfile = pidfile
17
18 def daemonize(self):
19 """
20 do the UNIX double-fork magic, see Stevens' "Advanced
21 Programming in the UNIX Environment" for details (ISBN 0201563177)
22 http://www.erlenstar.demon.co.uk/unix/faq_2.html#SEC16
23 """
24 try:
25 pid = os.fork()
26 if pid > 0:
27 # exit first parent
28 sys.exit(0)
29 except OSError, e:
30 sys.stderr.write("fork #1 failed: %d (%s)\n" % (e.errno, e.strerror))
31 sys.exit(1)
32
33 # decouple from parent environment
34 os.chdir("/")
35 os.setsid()
36 os.umask(0)
37
38 # do second fork
39 try:
40 pid = os.fork()
41 if pid > 0:
42 # exit from second parent
43 sys.exit(0)
44 except OSError, e:
45 sys.stderr.write("fork #2 failed: %d (%s)\n" % (e.errno, e.strerror))
46 sys.exit(1)
47
48 # redirect standard file descriptors
49 sys.stdout.flush()
50 sys.stderr.flush()
51 si = file(self.stdin, 'r')
52 so = file(self.stdout, 'a+')
53 se = file(self.stderr, 'a+', 0)
54 os.dup2(si.fileno(), sys.stdin.fileno())
55 os.dup2(so.fileno(), sys.stdout.fileno())
56 os.dup2(se.fileno(), sys.stderr.fileno())
57
58 # write pidfile
59 atexit.register(self.delpid)
60 pid = str(os.getpid())
61 file(self.pidfile,'w+').write("%s\n" % pid)
62
63 def delpid(self):
64 os.remove(self.pidfile)
65
66 def start(self):
67 """
68 Start the daemon
69 """
70 # Check for a pidfile to see if the daemon already runs
71 try:
72 pf = file(self.pidfile,'r')
73 pid = int(pf.read().strip())
74 pf.close()
75 except IOError:
76 pid = None
77
78 if pid:
79 message = "pidfile %s already exist. Daemon already running?\n"
80 sys.stderr.write(message % self.pidfile)
81 sys.exit(1)
82
83 # Start the daemon
84 self.daemonize()
85 self.run()
86
87 def stop(self):
88 """
89 Stop the daemon
90 """
91 # Get the pid from the pidfile
92 try:
93 pf = file(self.pidfile,'r')
94 pid = int(pf.read().strip())
95 pf.close()
96 except IOError:
97 pid = None
98
99 if not pid:
100 message = "pidfile %s does not exist. Daemon not running?\n"
101 sys.stderr.write(message % self.pidfile)
102 return # not an error in a restart
103
104 # Try killing the daemon process
105 try:
106 while 1:
107 os.kill(pid, SIGTERM)
108 time.sleep(0.1)
109 except OSError, err:
110 err = str(err)
111 if err.find("No such process") > 0:
112 if os.path.exists(self.pidfile):
113 os.remove(self.pidfile)
114 else:
115 print str(err)
116 sys.exit(1)
117
118 def restart(self):
119 """
120 Restart the daemon
121 """
122 self.stop()
123 self.start()
124
125 def run(self):
126 """
127 You should override this method when you subclass Daemon. It will be called after the process has been
128 daemonized by start() or restart().
129 """
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